GMAT Question of the Day - Daily to your Mailbox; hard ones only

It is currently 18 Sep 2018, 22:19

Close

GMAT Club Daily Prep

Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track
Your Progress

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.

Close

Request Expert Reply

Confirm Cancel

If ab = b, which of the following must be true?

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:

Hide Tags

Manager
Manager
avatar
G
Joined: 28 Jun 2018
Posts: 125
Location: India
Concentration: Finance, Marketing
GPA: 4
GMAT ToolKit User Premium Member Reviews Badge CAT Tests
If ab = b, which of the following must be true?  [#permalink]

Show Tags

New post 27 Aug 2018, 01:11
1
00:00
A
B
C
D
E

Difficulty:

  35% (medium)

Question Stats:

55% (01:00) correct 45% (00:39) wrong based on 31 sessions

HideShow timer Statistics

If ab = b, which of the following must be true?

A) a=1
B) b=0
C) a=1 and b=0
D) a=1 or b=1
E) a=1 or b=0

_________________

What to do if you are new to GMAT:
https://gmatclub.com/forum/what-to-do-if-you-are-new-272708.html#p2108758

GMAC official guides : https://gmatclub.com/forum/gmac-official-guides-the-master-directory-links-240610.html#p1854935

Give me kudos if you like it , it's totally harmless :)

Math Expert
User avatar
V
Joined: 02 Aug 2009
Posts: 6786
Re: If ab = b, which of the following must be true?  [#permalink]

Show Tags

New post 27 Aug 2018, 01:16
1
1
GMATbuster92 wrote:
if ab=b , which of the following must be true?
A) a=1
B) b=0
C) a=1 and b=0
D) a=1 or b=1
E) a=1 or b=0


\(ab=b........ab-b=0........b(a-1)=0\)
so a=1 or b=0 or both

E
_________________

1) Absolute modulus : http://gmatclub.com/forum/absolute-modulus-a-better-understanding-210849.html#p1622372
2)Combination of similar and dissimilar things : http://gmatclub.com/forum/topic215915.html
3) effects of arithmetic operations : https://gmatclub.com/forum/effects-of-arithmetic-operations-on-fractions-269413.html


GMAT online Tutor

Intern
Intern
avatar
B
Joined: 11 Nov 2017
Posts: 39
Location: Belgium
Concentration: Technology, General Management
GMAT 1: 670 Q47 V34
GMAT 2: 750 Q50 V41
GMAT 3: 750 Q50 V41
GPA: 2.5
WE: Engineering (Aerospace and Defense)
Re: If ab = b, which of the following must be true?  [#permalink]

Show Tags

New post 27 Aug 2018, 01:20
fairly straightforward:

ab=b

any number multiplied by 1 remains the same:
1.b=b
--> a=1
there is no other option for a to be anything else since that would modify the outcome

then ask yourself: is there an option where b on it's own can make this true:
the only case where any variable number of times a number = that number is for 0
1.b=b
2.b=b
3.b=b
is only ever true for b=0

since we figured out these 2 requirements a=1, b=0 separately, this means there is no dependency, hence:
OR

a=1 or b=0

--> E

kudos if this helped
Re: If ab = b, which of the following must be true? &nbs [#permalink] 27 Aug 2018, 01:20
Display posts from previous: Sort by

If ab = b, which of the following must be true?

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  

Events & Promotions

PREV
NEXT


GMAT Club MBA Forum Home| About| Terms and Conditions and Privacy Policy| GMAT Club Rules| Contact| Sitemap

Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne

Kindly note that the GMAT® test is a registered trademark of the Graduate Management Admission Council®, and this site has neither been reviewed nor endorsed by GMAC®.